The 20-year plan, which targets 117 acres around Union Square, will include the development of residential, commercial and green space in an effort to revive Somerville’s “downtown.”

Click to enlarge — Parcel A-3 will be transferred to the MBTA for construction of the Union Square Green Line station. (City of Somerville)

The city plans to acquire seven blocks around Union Square over several years, the first being the block bounded by Prospect Street, Somerville Avenue and Allen Street, where the MBTA plans to open a Green Line station.

Green Line Extension

“This is the culmination of several years of dedication and hard work, and with the recent agreement with the state and MBTA, this plan presents the most economically sound plan for our city’s sustainable future,” Somerville Mayor Joseph Curtatone wrote in a statement.

The state is legally obligated to extend the Green Line to Somerville and Medford to offset the environmental impacts of the Big Dig. Originally set to be complete in 2011, the extension has been delayed for years.

Union Square MBTA station renderings. (City of Somerville)

Construction is currently slated to start in spring of 2014 with the completion of a “operational transit station” in Union Square by late 2016 or early 2017.

Private And Public Redevelopment

While most of the “revitalization district” will be open to private redevelopment, the city also plans to build a $43 million library on Washington Street near Merriam Street.

In the plan, the city expressed hope that the Union Square will follow in the footsteps of Assembly Square, where an Orange Line station is currently in development along with four surrounding blocks.

The plan still needs to be approved by Somerville’s Board of Alderman and the state’s Department of Housing and Community Development.